Tracker requirements

[Condor68]

There has been aa aircraft circling this area a large part of the afternoon according to my neighbour. It is probably for the Press/TV coverage for the Womens Open Golf which starts tomorrow.I am just wondering why it isnt showing up on ADSB FR24 or Feedar.I would have thought being quite close to Dundee Airport they would need the Tracker switched on.WE also quite often get Fast Jets nipping along over here at very low level so I would think the tracker would be mandatory here.The three systems were all showing different results.What have I missed????

Cheers

Keith

[Alf]

There has been aa aircraft circling this area a large part of the afternoon according to my neighbour. It is probably for the Press/TV coverage for the Womens Open Golf which starts tomorrow.I am just wondering why it isnt showing up on ADSB FR24 or Feedar.I would have thought being quite close to Dundee Airport they would need the Tracker switched on.WE also quite often get Fast Jets nipping along over here at very low level so I would think the tracker would be mandatory here.The three systems were all showing different results.What have I missed????

Cheers

Keith

By "the Tracker" assume you mean their Mode-S transponder? Would have though all flights now use this unless switched off for a reason.

[Condor68]

Thats what I mean I would have thought in an area that covers Leuchars Dundee Airport and a low level flying area,they would be on all the time.We get quite a lot of small to medium civils over here and a lot of them dont show up. I would have thought it would mandatory to have them on.

[Mike]

ATC will be able to see them - so no problems there!
Quite a lot of civilian aircraft only show on trackers at above 2 or 3 thousand feet due to the transponders that they have - just find any Loganair aircraft on FR24 and most will disappear from view about 10 or 20 miles out from it's destination! There are loads of other examples.
Military aircraft can switch off their ability to be seen on trackers, it's because they're military and the general public shouldn't really be able to watch their every move!

[Malcolm]

There has been aa aircraft circling this area a large part of the afternoon according to my neighbour. It is probably for the Press/TV coverage for the Womens Open Golf which starts tomorrow.I am just wondering why it isnt showing up on ADSB FR24 or Feedar.I would have thought being quite close to Dundee Airport they would need the Tracker switched on.WE also quite often get Fast Jets nipping along over here at very low level so I would think the tracker would be mandatory here.The three systems were all showing different results.What have I missed????

Cheers

Keith

C-12 "G-FPLD" is showing on PP in the Leuchars overhead at 500ft. Dunno if that's your bird.

To answer your question.

1) All the Tracking sites rely on 'civilian' users with their own ADSB receivers uploading regular reports to a central server. The server then aggrigates all these reports, and generates a web page for you to see. The websites don't get any 'official data' feeds (AFAIK) direct from real radar operators (like Leuchars or Dundee airport, or Scoittish Mil, or RAF or MOD or NATS etc). So the websites only see whatever one or more of their uploaders see and it all depends on how good the coverage is - effectively how many uploaders there are in your area. Stuff at low level will not be seen by anyone more than a few tens of miles away whereas airliners at FL400 can probably be picked up by anyone within a 200+ miles.

2) There are two forms of ModeS - ModeS+ADSB enabled and plain ModeS (no ADSB). ModeS+ADSB enabled means the aircraft can report it's GPS position. ModeS only means it only gives altitude and Squawk. Most Civil planes are full ModeS+ADSB. Many Military are basic ModeS only, or routinely fly with the ADSB bit turned off. To plot the position of a non ADSB aircraft from it's other ModeS replies you need special triangulation software called MLAT. Not many web based trackers support MLAT, so military aircraft flying with ADSB turned off don't show because even if you know the plane is up there somewhere, you've no idea where to put it on the map. The triangulation also needs a minimum of 3 sharers to be seeing the aircraft to get a fix. Real radar sites (Leuchars & Dundee) don't need to MLAT because they've got a real radar pointed in a known direction, so they know something is out there, and the Mode S replies are synchronised to the sweep of the radar dish so they can tie up callsign, altitude and squawk to a blip on the screen.

3) Military flights often don't use ModeS at all. There is no legal international requirement for State Aircraft to be fitted with or use ModeS/ADSB. Individual states can of course insist on it, but the UK generally doesn't. Some types are fitted with ModeS+ADSB, but routinely fly with it all turned off. If ModeS is turned off, then generally speaking the sharers can't 'see' the plane at all, so there is nothing to upload to the server, so nothing appears on the web page. Most (all?) Military types do fly with legacy SSR modes 3A and 3C enabled, so real radar sites (like Leuchars, Dundee) can see these codes on their screens, as can users of certain (superior) tracking software.

4) There are also some civilian "spy" aircraft that get up to unspecified actions, and one of their haunts is off the coast of Dundee. These often fly with their ModeS/ADSB transponders turned off, presumably to try and hide from the tracking sites so they can do what they do without those that they are observing knowing. Aledgedly.

5) Finally, not sure on the exact rules, but there is a weight limit below which ADSB transponders aren't mandatory in light civils. Microlights, Firewood, Puddle jumpers etc.

[Condor68]

Thanks for taking the tme to reply Malcolm its a bit more complex than I thought.

Keith

[Mike]

It's really not complex, I think that you're under the impression that Air Traffic Control are looking at the same info that is on trackers like FR24 that the general public can use. This is not the case, they use a proper radar system that shows every aircraft.

[Condor68]

I realised the real radars would pick things up Mike,it was the different types and modes plus weight possibly being brought into the equation I thought was complex.Sorry I should maybe have worded the post a bit better.

Keith

[slogen51]

At Old Buckenham airfield in Norfolk last year the controller in the PortaKabin was looking at Planefinder on a computer screen